Mendeley - Easily organize your papers, read & annotate your PDFs, collaborate in private or open groups, and securely access your research from everywhere.

Ubersuggest - Want more traffic? Ubersuggest shows you how to win the game of SEO. Just type in a domain or a keyword to get started.

Zotero - Zotero is a free, easy-to-use tool to help you collect, organize, cite, and share research.

SERPstash - Free SEO tools for Entrepreneurs

Qiqqa - Qiqqa is a free research and reference management software. It can be used in many organizational projects from the academic to the personal to the business endeavor. Read more about Qiqqa.

Serpstat - Search analytics, Rank tracking, Backlink analysis and Site Audit tool.